Hundreds of people marched outside Brayton Point Power Station in Somerset on Sunday.

The protest was organized by 350MA in an effort to convince Massachusetts Governor Deval Patrick to shut down New England’s largest fossil-fueled power producer and opt for cleaner energy instead.

The Patrick administration has set a target of getting more than a quarter of the Commonwealth’s electricity needs from renewable or alternative sources by 2020.

The Bottom Line

Is shutting down Brayton Point even a possibility? Short answer – no. The Patrick administration has set a target of getting greater than 25 percent of Massachusetts' energy from renewable or alternative sources - wind, solar, hydro, biomass – by the year 2020. But a statement provided by the Office of Energy and Environmental Affairs makes it clear that doesn't necessarily mean taking older fossil-fueled power plants offline:

“Under Governor Patrick’s leadership, Massachusetts has established the most aggressive greenhouse gas reduction goals in the nation, earned the number one ranking in energy efficiency two years in a row, and is an active participant in the Regional Greenhouse Gas Initiative (RGGI). We also continue to pursue renewable energy sources aggressively in order to diversify our portfolio and provide clean, homegrown energy sources in Massachusetts. Meanwhile, energy reliability remains critical to the economy and our citizens’ well-being. While we anticipate that coal will become a declining percentage of the Massachusetts resource mix, and the percentage of clean renewables will increase, we are working to ensure that we achieve our goals without jeopardizing reliable energy supply.”

The Reliability Factor

When they say "reliable," they mean oil- and/or coal-powered. The sun doesn't shine at night, and the wind doesn't blow 24/7. So renewables require companion sources to fill gaps and ensure that the light comes on when you flip the switch.

There has been a steep decline in oil and coal use in recent years. In 2010, oil and coal fueled 40 percent of New England's energy production. That number is now less than 5 percent, according to ISO New England's 2013 Regional Electricity Outlook. And the number of new coal-fired plants being built has nose-dived in recent years.

Natural gas has taken up the slack, now accounting for 48 percent of Massachusetts power. ISO New England says that's resulted in lower energy costs and reduced emission rates for greenhouse gases, including nitrogen oxides, sulfur dioxide, and carbon dioxide.

But there's a downside. The pipelines that bring natural gas to New England can be unreliable. ISO New England cites over-reliance on natural gas and aging oil/coal infrastructure as #1 challenge facing New England’s energy system

The Sunny Side

Progress toward the Patrick administrations renewable energy goals hasn't been what was expected - in both positive and negative ways. Wind energy development has been slower than hoped, but solar has exploded.

In May, state officials announced that the solar goal set in 2007 of 250 megawatts of residential and commercial solar energy installed in the Commonwealth had already been reached - four years early - and set an ambitious new goal of 1,600 MW by 2020.

Environment America released a report last week that ranked Massachusetts 7th in cumulative installed solar cpacityamong states, and cited the Commonwealth as an example of "set(ting) ambitious but achievable goals and back(ing) them up with policies that work."

The Nuclear Option

Where nuclear power fits into the clean energy picture depends on your perspective. It's a low-carbon energy source, but comes with public safety concerns and a waste disposal conundrum. Reliability (yep, we're back to that again) has also been an issue here in Massachusetts.

Pilgrim Nuclear Power Station has had a number of problems over the past couple of years. The most recent incident has an ironic twist to it. The heat wave that stifled New England earlier this month, prompted peak electricity demand and sent water temperatures in Cape Cod Bay over the 75F mark. As a result, Pilgrim - which uses that water to cool its reactors - had to power down to 85 percent production.

It's the first time in forty years of operation that that's happened, but as global temperatures rise, it's likely not the last.

Getting into the Mix

There are a number of other alternative energy sources that are making their way into Massachusetts' energy portfolio. With state waters covering an area 1/5 the size of the entire state, ocean energy is one to keep an eye one. There's also hydro-electric and biomass burning.

But here's one that's a bit off the beaten track. Earlier this month, the Patrick administration proposed a ban on commercial food waste disposal to take effect by July 1, 2014. If adopted, the measure would require any entity that disposes of at least one ton of organic waste per week to find a use for edible food and ship any remaining food waste to an industrial composter, an animal-feed operation, or - and here's the energy angle - an anaerobic digestion facility, where bacteria could turn leftovers into electricity.

Heather Goldstone is WGBH’s science editor. Our weekly conversations are part of our Living Lab Radio project. Major support for the Living Lab is provided by the Grantham Foundation for the Protection of the Environment.